California Department of Fish and Wildlife (CDFW) biologists and the Commercial Salmon Trollers Advisory Committee are continuing an experimental project to help California’s ocean-bound juvenile salmon, in hopes of increasing survival rates. On April 8, for the third year, CDFW staff will fill a boat with approximately 100,000 young Chinook (called smolts) and move it down the Sacramento River to San Francisco Bay. Upon arrival, the smolts will be released in the Bay, where they will swim into the sea and grow to adulthood before returning upriver to spawn.
The experimental project is being conducted by CDFW fisheries biologists with the support of the Commercial Salmon Trollers Advisory Committee, which donated the use of the boat, fuel and crew time to help ensure a successful start to the study. They have committed to helping CDFW continue data collection. The fishing vessel Merva W will receive 100,000 smolts into its hold in Rio Vista on the Sacramento River the morning of April 8.
This year’s severe drought has only exacerbated the number of challenges facing salmon smolts migrating downstream. Salmon return to their spawning grounds using their sense of smell. The process, called imprinting, begins before birth as waters flow over the eggs and continues as they grow and make their way to the ocean. Each segment of water on their journey has distinctive chemical cues which they can re-trace to their spawning grounds. Water is circulated through pumps from the Sacramento River into the Merva W ‘s holding tank, where the fish are kept. The hope is that this may improve their ability to find their way back as adults. The trucking process also prevents that smolts from exposure to predators during the journey downstream.
This is the third year of a three-year experimental project to determine if barging improves smolt survival. Data collected over the next few years will be evaluated to determine if these fish had higher survival rates, if more of these fish make it back to the hatchery of origin and how this release strategy differs from others currently being used.
To form a basis of comparison for the experimental project, two other control groups of 100,000 smolts each will be released by trucks in other locations at the same time as the barge release — one under the Golden Gate Bridge and one into the Sacramento River near Rio Vista. All 300,000 fish in this experimental project are implanted with coded wire tags smaller than a tiny piece of pencil lead, which will ultimately enable scientists to tell which of the three groups the returning fish came from — the barge release, or one of the two truck releases.
Data collected from this experiment will help scientists to evaluate the efficiency of barging when compared to other release strategies, as well as to determine which group has better survival rates and how quickly the fish make it back to their natal hatcheries (improved stray rates).
The city of Rio Vista and the Tiburon Salmon Institute at the Romberg Center are providing access for the transport boat and fish trucks.
Andrew Hughan, CDFW Communications, (916) 322-8944
Bill Smith, Hatchery Manager, (209) 759-3383